Headlight high beams on a car are a useful tool. When used incorrectly, however, they can cause harm to yourself and to other drivers--day or night. It's critical to understand the rules of high beams to help prevent a serious accident, injury and possibly death.
Oncoming Next-Lane Traffic
When you're on a dark road at night, you need your high beams so you can spot deer, other animals and unexpected curves in the road. However, when another car is coming toward you in the opposite lane, you need to turn your high beams off at least 500 feet from the car. High beams are too bright and can distract an oncoming driver. As soon as the driver passes, you can turn your high beams on again as long as there isn't another car coming.
Oncoming Median-Separated Traffic
If you have your high beams on at night and you're on a road on which the two sides of the road are separated by a median, you don't have to turn your brights off if the oncoming drivers stay a minimum of 500 feet from you while passing. Many drivers do, however, turn the high beams off out of common courtesy. You never know when a beam is going to hit you just the wrong way, so it's never a bad idea to turn your brights off for another driver, even if you aren't required to.
Daytime High Beams
During the day, high beams are always more distracting for oncoming traffic than helpful, especially on sunny days. Turn them off unless it is dark and/or rainy, and in this case, use Sections 1 and 2 protocol. It is becoming popular for motorcycle driver to keep high beams on during the day, but this practice can be dangerous, as motorcycle beams can be distracting to drivers.